I have three small bottles for right now (4 month old) I wash them immediately after I use them. I have 4 large ones for when she starts eating more than 4oz at a time.

I bought Tommee Tipee bottles and my DD hated them, she will only use Advent. So, I say don't stock up lots on one particular brand until you know what your LO will take.

Also, I thought I was being super smart and stockpiled formula. I mean....cans & cans and formula. Ultra prepared. She's allergic to milk and soy, and all the cans we bought she can't use. All the regular formulas are pretty much the same and that is what I would start on.